DP83867E: MDI and MII Inter-pair vs Intra-Pair Skew Requirement

Hi Hamza,

For the MDI this refers to the intra-pair skew (the skew between the positive and negative lines in a differential pair).  

For the MII this refers to the skew between all RX signal lines and the skew between all TX signal lines. TX lines do not need to be matched to RX lines.

• For example: RX_D0 should be within 20 mils of RX_D1, RX_CLK, RX_CTRL,... RX_D0 does not need to match TX_D0.

Best,

Shane

We recommend keeping all MDI traces under 2" of length. If you can keep inter-pair skew within 20mils as well I recommend doing so.

Best,

Shane

Hi Hamza,

DP83867 has internal RGMII terminations on the PHY's transmitters, so external series terminations are optional for these lines. The internal RGMII terminations can be adjusted in the IO_IMPEDANCE_CTRL register located in address 0x170[4:0]

Please note these are only valid for the RGMII outputs on DP83867 (RX_CLK, RX_D0/1/2/3, RX_CTRL,...). We cannot adjust the terminations on the RGMII inputs as these are only receivers internally. You may need to add external terminations on the RGMII TX path (TX_CLK, TX_D0/1/2/3, TX_CTRL,...)

Best,

Shane